Signal lamps are typically employed to generate one or more optical signals that indicate possible hazards, special conditions, etc. For example, signal lamps are used to signal or provide a warning about, for example, malfunctions in machines. However, signal lamps can just as well indicate escape routes, or sometimes even display advertising. This applies in the case of acoustic signaling devices that can also qualify as electrical signal circuit assemblies as defined above.
Whenever, by way of example, light sources are mounted on a circuit board composed of a heat-conducting material, the problem of dissipating the heat arises in connection with special applications. This is true specifically in the case of electrical circuit assemblies in general, and specifically for signal lamps that are used in locations at risk of explosion, that is, what are called explosion-protected electrical (signal) circuit assemblies, or signal lamps, or even signaling loudspeakers. Signal lamps of this type on the one hand have a pressure-tight encapsulation of the housing, with the result that the dissipation of waste heat is a problem. Alternately, the housings are filled either completely or to a substantial degree with a potting compound, with the result that analogous problems arise since this type of potting compound typically has extremely poor thermal conductivity.
The above-referenced problem thus applies in general for all housings of signal lamps, since an increase in the accumulation of waste heat must be expected due to the generally high luminous intensity of the light sources. Inside the housing, this waste heat can result in an increase in temperature relative to the surrounding ambient temperature. The increased temperature inside the housing renders the use of signal lamps problematic in the case of the example involving locations at risk of explosion. This is because there is the risk of heating up certain parts of the housing to a significantly higher temperature than other parts. As a result, what are known as hot spots are observed on the surface of the device that can present a source of ignition for the surrounding atmosphere in locations at risk of explosion.
This is true not only in the case of certain mixtures of gas or when ignitable gases occur, but also, for example, in the case of combustible dust when powder is processed. What must also be taken into account as an additional factor in this situation is the fact that the smaller the distance between the heat source and the surface, the higher is the partial heating due to radiation and convection. This means that the occurrence of the above-described hot spots is enhanced by the small spacing between the heat source and the surface, and by the insufficient dissipation of heat from the surface.
For these reasons, the analogous prior art according to GB 2,428,467 has a projecting cooling element for an explosion-protected signal lamp. The cooling element or cooling block is in contact with the surrounding atmosphere. The circuit board including LEDs mounted thereon is located on the cooling element or cooling block. The circuit board itself is made of aluminum or another suitable material of high thermal conductivity.
The fact that the circuit board in the prior art must be mounted, or is mounted, with its mounted LEDs directly on the cooling block, necessarily means that the possible embodiments in terms of the design of the signal lamp are limited. In particular, it is virtually impossible by this approach to create cylindrical or very tall signal lamps that are equipped with a slender, long housing. The goal of the invention is to provide a remedy for this.